Relatively large glass panels are used in the manufacturing of flat panel televisions, among other applications, in addition to much smaller panels for use in devices such as cell phone screens. During manufacturing, the glass is heated by a heater that is placed directly onto or proximate the surface of the glass. Often, the heater is custom designed for the specific size of the glass panel and thus for different sizes of glass, a heater is redesigned as a separate, unitary heater panel for each different glass size. Thus each size of glass panel has its own separate heater. Additionally, these separate, unitary heaters become larger and larger with larger glass panel sizes.
In some heater applications for these relatively large glass panels, the unitary heater is divided into sections or tiles that can be independently controlled in order to provide a different power distribution across the glass panel. Although each section can be independently controlled for a more tailored heat distribution, the heater remains unitary and is custom designed for the size of the glass panel that is being processed. Accordingly, a separate heater is used for each glass size, and thus a plurality of glass sizes results in a plurality of individual heaters.
Layered heaters are often used in the processing of these glass panels. A layered heater generally comprises layers of different materials, namely, a dielectric and a resistive material, which are applied to a substrate. The dielectric material is applied first to the substrate and provides electrical isolation between the substrate and the electrically-live resistive material and also minimizes current leakage to ground during operation. The resistive material is applied to the dielectric material in a predetermined pattern and provides a resistive heater circuit. The layered heater also includes leads that connect the resistive heater circuit to an electrical power source, which is typically cycled by a temperature controller. Further, the layered heater may comprise an over-mold material that protects the lead-to-resistive circuit interface. This lead-to-resistive circuit interface is also typically protected both mechanically and electrically from extraneous contact by providing strain relief and electrical isolation through a protective layer. Accordingly, layered heaters are highly customizable for a variety of heating applications.
Layered heaters may be “thick” film, “thin” film, or “thermally sprayed,” among others, wherein the primary difference between these types of layered heaters is the method in which the layers are formed. For example, the layers for thick film heaters are typically formed using processes such as screen printing, decal application, or film printing heads, among others. The layers for thin film heaters are typically formed using deposition processes such as ion plating, sputtering, chemical vapor deposition (CVD), and physical vapor deposition (PVD), among others. Yet another series of processes distinct from thin and thick film techniques are those known as thermal spraying processes, which may include by way of example flame spraying, plasma spraying, wire arc spraying, and HVOF (High Velocity Oxygen Fuel), among others.